The present invention relates to an apparatus for precise measurement of optical characteristics, and particularly to an optical characteristic measuring apparatus comprising a position change unit for changing the positions of beams transformed by a first transforming member.
Among optical characteristic measuring apparatuses, there has been an apparatus disclosed in a patent application made by the present applicant, in which the focus in an illumination optical system is adjusted based on a light reception level of a first light receiving unit and the focus of a light receiving optical system is adjusted based on an optical characteristic (S) determined from an output of the first light receiving unit (Japanese Patent Application No. 9-137630 (1997)).
In addition, the present applicant has applied an apparatus for measuring optical characteristics by use of a plurality of beams by a beam transforming member known as a Hartmann plate (Japanese Patent Application No. 9-42940 (1997)).
However, in order to measure with high precision, it is necessary to use a transforming member with a high density of openings. In a transforming member with a high density of openings, the quantity of light for one opening is small. Besides, there is the drawback that when one opening is reduced, the size of the lens comes to be on the same order as a diffraction limit image. As a result, there is the problem that, depending on the positional relationship between adjacent spots, it is impossible to specify the spots.
The present invention may resides in that a first light source emits a luminous flux of a first wavelength, a first illumination optical system illuminates a minute area on the retina of an eye under examination by the luminous flux from the first light source, a first light receiving optical system leads light to a first light receiving unit through a transforming member for transforming the luminous flux having undergone at least one of transmission and reflection at at least one surface of the object of measurement into at least nine beams, a position change unit changes the positions of the beams transformed by the first transforming member, and an arithmetic unit can determine optical characteristics of the object of measurement based on a first signal from the first light receiving unit corresponding to the angle of inclination of the luminous flux.
In addition, the position change unit according to the invention may change the positions of the beams transformed by the first transforming member by at least one of linear movement and rotational movement of the first transforming member.
Besides, the position change unit according to the invention may move the first transforming member to at least one of mechanical constitution and optical constitution.
Further, the position change unit according to the invention may change the positions of the beams transformed by the first transforming member by at least one of linear movement and rotational movement of the first transforming member, whereby the transformed beam positions after the change are located at roughly middle positions of the transformed beams before the change.
In addition, the arithmetic unit according to the invention may calculate optical characteristics of the object of measurement based on data before and after the change of beam positions, and may determine a process according to the deviations of the optical characteristics.
Further, the arithmetic unit according to the invention may prompt re-measurement based on the data before and after the change of beam positions when the optical characteristics of the object of measurement calculated respectively based on the data before and after the change are discrepant from each other by not less than a predetermined value.
Besides, the arithmetic unit according to the invention may determine measurement results through mean values of optical characteristics based on the data before and after the change of beam positions when the optical characteristics of the object of measurement calculated respectively based on the data before and after the change are within predetermined values.
In addition, the arithmetic unit according to the invention may determine measurement results based on data obtained by synthesizing the data before and after the change, based on the data before and after the change of beam positions, when the optical characteristics of the object of measurement calculated respectively based on the data before and after the change are within predetermined values.
Further, the present invention may resides in that the object of measurement is an eye under examination, the at least one surface of the object of measurement is the cornea surface, the first illumination optical system illuminates the cornea, the first light receiving optical system receives light through the first transforming member for transforming the luminous flux reflected by the cornea surface into at least nine beams, and the arithmetic unit can determine the shape of the cornea of the dye under examination as optical characteristics of the object.
Besides, the present invention may resides in that the object of measurement is an eye under examination, the at least one surface of the object of measurement is the retina, the first illumination optical system illuminates the retina, the first light receiving system receives light through the first transforming member for transforming the luminous flux reflected by the retina into at least nine beams, and the arithmetic unit can determine the refracting power of the eye under examination as optical characteristic of the object.
In addition, the present invention may resides in that the object of measurement is an optical lens, the first illumination optical system illuminates an illumination luminous flux such as to transmit through or be reflected by the optical lens, and the first light receiving optical system can receive light through the first transforming member for transforming the illumination luminous flux having transmitted through or been reflected by the optical lens into at least nine beams.
Further, the present invention may resides in that at least two kinds of the first transforming member are provided, a changeover from one of the first transforming members to the other of the first transforming members is carried out by linear movement or rotational movement, and the first transforming member thus changed over can be inserted into an optical path.